1. Field of the Invention
The present invention relates generally to a diaphragm actuator, and more specifically to a multiple diaphragm actuator for exerting forces of precise and repeatable amounts in opposite directions with no friction and with no fluid leakage. The invention also relates to a multiple diaphragm actuator for applying a linear force in opposite directions at a point positioned entirely to one side of the actuator.
2. Description of the Prior Art
A variety of what are commonly referred to as diaphragm actuators exist in the art for applying a force to a work piece. A common actuator of this type includes a pair of pressure chambers separated by a diaphragm with means for selectively introducing fluid pressure into, and exhausting fluid pressure from, the pressure chambers. Commonly associated with the diaphragm is an elongated actuator rod which is movable with the diaphragm. This rod extends through one of the pressure chambers and through a sealed opening in the pressure chamber to a work piece. With this type of actuator, forces exerted on the diaphragm and thus the actuator rod by the pressure chambers are controlled by selective introduction and exhaustion of fluid pressure into and out of the opposed pressure chambers. However, several potential problems exist with this design: First, friction and potential for leakage exist between the actuator rod and the seal members which seal the rod as it exits the one chamber. Whenever there is a possibility of friction and/or leakage, extreme accuracy and repeatability are virtually impossible. Second, the seal members sealing the rod as it exits the one chamber will eventually wear-out and thus need replacement. This results in further inaccuracy and non-repeatability. Thirdly, the volumes of the two opposing chambers are not exactly matched because of the existence of the rod in the one chamber and because the amount of the rod within the one chamber varies as the chamber expands and contracts. This again adversely affects the accuracy of the forces generated on the rod and the repeatability of force generation. Accordingly, with known diaphragm actuators such as those described above, extremely accurate and repeatable forces are difficult, if not impossible, to achieve.
Accordingly, there is a need in the art for an improved diaphragm actuator which is capable of providing extremely accurate and repeatable forces and which virtually eliminates any inaccuracies and any repeatability concerns resulting from friction or leakage of fluid from the pressure chambers.